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Questions tagged [digital-modes]

Transmission of digital signals over Amateur Radio, including modes like PSK-31, RTTY, JT-65, JT-9, etc.

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Is there a disadvantage to using a cheap HT for APRS?

Looking to build a cheap (not even inexpensive, just dirt cheap) APRS beacon transmitter. Right now you can get a dual band handheld transceiver with rechargeable battery, antenna, etc for under $31 [...
Adam Davis's user avatar
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15 votes
11 answers
7k views

Is Morse code a digital, binary mode?

At first glance Morse code looks like a digital mode - there are dits and dahs, two values which contain the information of the transmission. Alternatively, at any point in time there either is a ...
DK2AX's user avatar
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13 votes
3 answers
780 views

What is the role of digital data modes in emergency communications?

Emergency operations are typically reliant on voice traffic today. Are digital data modes used at all in emergency operations, and why/ why not? Couldn't data modes be used to pass information more ...
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12 votes
4 answers
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What is generally considered "too much" power for JT-65 on HF?

Recently, I have begun experimenting with JT-65A, mostly on 20 meters. I usually run about 5 watts with that mode, since I know that JT-65 is a weak-signal mode. Is that still too much power? What is ...
krzysz00 KF5SOQ's user avatar
12 votes
1 answer
6k views

How do I discover APRS coverage?

I'm considering adding simple APRS transmitters to my vehicles. I'd rather just put one in and forget about it, but I understand there are areas of the US where a stronger transmitter would be ...
Adam Davis's user avatar
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11 votes
6 answers
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What transfer rates are actually achievable using known digital modes?

I've found all sorts of info concerning digital modes, sound samples, spectrum samples, but nobody ever cites what speed a given digital mode can reach. Could anyone tell me more about that, or point ...
red-o-alf's user avatar
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11 votes
3 answers
1k views

Are hashes (such as md5) legal in the US

If I were to implement a remote computer control system using amateur radio, would using hashes (such as md5, sha-*, etc...) for authentication be permissible under the United States rules?
W8AWT's user avatar
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11 votes
2 answers
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Can an amateur use cellular technologies with SDR?

Software Defined Radio is opening up many new possibilities for amateur digital modes. One family of technologies that interests me is cellular. 2G GSM voice/sms and 2.5G GPRS data has been proven to ...
JC Hulce's user avatar
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10 votes
2 answers
1k views

Moon->Earth 433MHz link achievable digital bandwidth

Let's assume we have the following situation: Transmitter on moon orbit (distance from earth ~400'000km), around 433Mhz. Transmitter power 1W, antenna gain 10dB, circular polarization. Steered to ...
BarsMonster - R2AYN's user avatar
10 votes
2 answers
3k views

Am I really receiving FT8 signals from 12,000 km away on 144 MHz?

I have been using an Ettus B200 SDR to receive FT8 transmissions in the 2-meter band (144.174 MHz) using the WSJT-X software. Signals are received using a telescopic antenna inside on a window ledge ...
David's user avatar
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10 votes
2 answers
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Do FCC regulations limit digital data rate?

Are there FCC regulations that specifically limit digital data rate on the amateur bands? Are there any recent or proposed changes? If so, what are they specifically?
Phil Frost - W8II's user avatar
10 votes
4 answers
482 views

How to operate on HF if an AM transmitter is only 540 feet away?

I'm a General Class Licensee, and due to pulmonary disease I cannot operate voice. I am also about 540 feet from a 24/7 1 kW AM station. The signal is so pronounced that most audio devices in the ...
Gordon C's user avatar
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10 votes
2 answers
3k views

What is a fixed digital message forwarding system?

What is a fixed digital message forwarding system? I noticed this on the lower end of the 222MHz allocation in the US but it's not explained on the band chart:
Adam Davis's user avatar
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10 votes
2 answers
992 views

Getting Started with Digital Modes on VHF on Linux

I am interested in learning about digital modes using 2m and Linux. I have a couple of older 2m rigs (HTX-212 and an old Yaesu) with no additional hardware, like a TNC. What current resources exist ...
Rob Gibson's user avatar
10 votes
1 answer
342 views

How can I do direct digital synthesis of a 630m WSPR signal?

I want to do direct digital synthesis of a 630m band WSPR signal. Specifically I'd like to use an Atmega 328 chip running at 20 MHz to produce such a signal. I will use standard phase accumulator ...
Eric Urban's user avatar
9 votes
4 answers
18k views

2m or 70cm FM mobile radio for digital mode operation

Are there any 2m and/or 440cm FM mobile radios that have audio inputs for supporting digital modes, like PSK31 or SSTV? I have a Rigblaster that I use with my HF radio so I could get a mike cable and ...
Kevin Hooke KK6DCT's user avatar
9 votes
1 answer
2k views

Digital-mode signal reports

When operating analog voice, we give a qualitative (or possibly just arbitrary) signal report, 'scoring' the signal either out of a maximum 'five by five', or a maximum '599'. How do you report the ...
Dan KD2EE's user avatar
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8 votes
7 answers
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What does sending SK after calling CQ mean?

When I was at a local radio club today, I witnessed a bit unusual response by a station calling CQ using BPSK31, that is to say phase-shift keying, not the regular A1A telegraphy, on the 20 meter band....
AndrejaKo's user avatar
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8 votes
2 answers
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How does signal strength relate to bandwidth?

Let's say I have a 25 W transmitter. First I transmit some SSB signal with 2500 Hz bandwidth (no audio compressor is used, etc...). Then I transmit a BPSK31 signal with at most 100 Hz bandwidth using ...
Aleksander Alekseev - R2AUK's user avatar
8 votes
1 answer
5k views

DMR / DSTAR / P25 Software Encode / Decode

The large VHF / UHF digital voice communication modes all require the same AMBE vocoder chip from dvsinc. This surface mount chip can be aquired standalone for a relatively high price or all of the ...
Skyler 440's user avatar
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8 votes
2 answers
4k views

HF Digital Mode Band Plan for the USA

I recently started playing with the digital modes, but have been frustrated with the difficulty in finding where certain modes are commonly used. Is there a digital mode band plan for the HF bands, to ...
PearsonArtPhoto's user avatar
8 votes
1 answer
568 views

What is the difference between MFSK64 and MFSK64L?

I noticed this after updating fldigi to decode a Voice of America Radiogram. The only thing I could find in the fldigi changelog was this: ...
Sterling N0SSC's user avatar
8 votes
1 answer
180 views

Can club stations register callsigns on the D-Star network?

Some of the members at my local radio club are interested in working with D-Star. Since the equipment is very expensive, it was proposed that the club purchase and operate one rig collectively. Is ...
mtrberzi's user avatar
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7 votes
3 answers
413 views

Has any computer been hacked over amateur radio digital modes?

We don't normally worry about security in ham radio, because we can't encrypt our transmissions anyway in the vast majority of cases. Some niche protocols support authentication of messages, but that'...
Someone's user avatar
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7 votes
1 answer
3k views

Is there a legal limit to the bandwidth of a signal used in the amateur bands?

While a normal voice channel is ~10kHz-15kHz in bandwidth, some digital modes can be significantly wider. Are there any legal restrictions on how much bandwidth I could use for amateur radio ...
Stack Tracer's user avatar
7 votes
1 answer
2k views

Confusion about radio-computer interfaces: TNC, CAT, TRRS, Wolphi Link, ...?

This is probably a very simple and stupid question, but I'm getting more confused over time. Perhaps it is a matter of terminology, but a unified resource differentiating and explaining the different ...
hamster's user avatar
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7 votes
3 answers
1k views

Store-and-forward capable satellites in operation?

The amateur satellite community used to have a small fleet of pacsat satellites (AO-16 and friends), which were capable of store-and-forward message passing: you could upload messages to the LEO ...
oh7lzb's user avatar
  • 2,391
7 votes
1 answer
163 views

Efficient BPSK31 amplification

I'm looking at making a portable system that can transmit BPSK31. I have a limited power budget, so I'm looking at trying to make my final power amplifier as efficient as possible. From my ...
W5VO's user avatar
  • 1,901
6 votes
2 answers
109 views

How does a digital demodulator know which level it is reading?

I have recently started getting into wireless digital communications and I read about QAM modulation. But I am a little confused as to how the receiving demodulator would know which symbol it is ...
YellowBadger's user avatar
6 votes
7 answers
9k views

Are there any commonly used digital modes that work with an FM transceiver?

Like many new hams, I have just one radio: an inexpensive 2m/70cm FM transceiver. It doesn't do SSB and it doesn't have a digital input. If I wire up a connection between the radio and my computer's ...
mrog's user avatar
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6 votes
2 answers
720 views

Is it possible for an amateur to transmit ATSC?

Amateur television has long used the NTSC (analog) television standards to transmit video and audio. Several years ago, the digital broadcast television transition made higher-quality television ...
JC Hulce's user avatar
  • 901
6 votes
1 answer
1k views

What is "Billion Code" for garage door openers from around 1996?

I've been trying to "hack" my garage door using an SDR (LimeSDR) for a high school physics project, and I have run into a snag. When I look at the signal and demodulate it using ASK in Ultimate Radio ...
Ben Newhall's user avatar
6 votes
2 answers
891 views

Filtering for PSK31 demodulation

What's the ideal filter for PSK31 demodulation? That is, something that minimizes ISI, while having a narrow bandwidth to reject adjacent channels, while being reasonably matched? Most PSK modes use ...
Phil Frost - W8II's user avatar
6 votes
2 answers
932 views

Troposcatter: really all that bad?

The previous question, Packet Radio at 100 miles and specifically, Phil's answer raised an interesting question: In a 50–100 km distance situation where Line-Of-Sight beams aren't an option for ...
Marcus Müller's user avatar
6 votes
1 answer
2k views

How to calculate UMTS bitrates?

Assuming: Radio frame Subdivided in 15 slots Number of chips: 38.400 Duration: 10 ms; each slots = 666.6 μs and has 2.560 chips Example of channels DPDCH (Dedicated Physical Data Channel) (UL) ...
beginningperl's user avatar
6 votes
1 answer
270 views

APRS: WIDEn-N vs. TRACEn-N

The suggested APRS digipeater path is WIDE1-1,WIDE2-1 for the most use cases. According to the specs, this ensures two retransmissions by fill-in / regular ...
Georg DO1GL's user avatar
6 votes
1 answer
289 views

Pre-transmission burst sent by fldigi

Every time I click on a PSK macro, before transmitting the message, fldigi outputs a burst of something for about a second. This is visible but not readable on my waterfall display. It wastes time ...
Andrew Rose's user avatar
5 votes
3 answers
1k views

Unidentified signals on FT8 frequencies

When I work in FT8 mode I often see signals like these: I couldn't identify these signals using SigiWiki nor managed I to decode them using WSJT-X. Though these signals seem to use 15 second frames. ...
Aleksander Alekseev - R2AUK's user avatar
5 votes
2 answers
173 views

Air gapped digital communications mode on VHF?

According to this question MCW (modulated continuous wave) is allowed on large portions of the VHF bands in the U.S. Is using MCW suitable for passing small amounts of digital data between 2 PCs or ...
hotpaw2's user avatar
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5 votes
5 answers
2k views

What about the digital mode ROS causes some to consider it spread spectrum?

The FCC disallows amateur spread spectrum communications below 220MHz. At the moment the relatively new digital mode, ROS, is considered, by some, to be spread spectrum. So this mode is getting ...
Adam Davis's user avatar
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5 votes
3 answers
590 views

Is compression "encryption" under FCC regs?

I read this question about digital signatures and FCC prohibitions on "obscuring" messages in amateur transmissions, and it cause me to think of something: the difference between encryption and ...
Zeiss Ikon's user avatar
  • 4,097
5 votes
4 answers
4k views

Requirements for 9600 baud

I want to setup a TCP/IP link between my friends house 7km away from me on 70cm. 1200 Baud is a bit slow, and we are looking into something with a faster data rate. I know normal audio does not ...
Skyler 440's user avatar
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5 votes
2 answers
167 views

Weak signal digital modes and clock synchronization

Why to some weak signal digital modes (jt9, jt65, etc.) require knowing a clock time? Does knowing this clock time provide any gain in signal detection ability? (lower required S/N?) What clock ...
hotpaw2's user avatar
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5 votes
1 answer
667 views

Receive Data on Specific Frequency

So if I were to build a simple AM radio transmitter just using say, my Arduino, an oscillator, and wire for an antenna (this is all crude I know, but work with me here) and use it to transmit data ...
user2278224's user avatar
5 votes
1 answer
3k views

maximum acheivable range on CB radio by ground wave? [duplicate]

I have 10 watt CB radio system & 0.64 lambda monopole antenna , I think it has a 5 dBi gain . what is the maximum acheivable range by ground wave in an urban area ? If I want to increase my ...
abduoman11's user avatar
5 votes
2 answers
123 views

LOS One-way radio system, 4km with at least 1000bytes/s

In order to track skydivers/BASE-jumpers with flysight I am looking for a one-way radio system to transmit the location data. System needs the following specifications: ...
wittrup's user avatar
  • 153
5 votes
1 answer
1k views

How can I generate a list of APRS IGates on 30m?

I am investigating using a Tiny Trak 4 with my portable HF radio to self-spot on SOTA activations via APRS on 30m. I usually self-spot via a text message. When I don't have any cell coverage, I can ...
Malcolm VE2DDZ's user avatar
5 votes
1 answer
475 views

Expected practices for one ham operating under another's privileges?

I understand that in the United States, amateur operators and even non-licensed persons may participate in domestic (and approved international) communications on bands they wouldn't normally be ...
natevw - AF7TB's user avatar
5 votes
1 answer
135 views

Checking if the frequency is in use for digital modes

On CW and phone, we are taught to ask if the frequency is in use before calling CQ. Is it correct to say that with digital modes, that is impractical, and you should just listen (over the bandwidth ...
gschro's user avatar
  • 157
4 votes
4 answers
14k views

How can I decode an AFSK 1200 baud audio clip? (ISS)

I'm a new ham. The past few days, I've had a few nearby passes of the International Space Station. As it was going overhead, I managed to record what I believe to be 1200 baud AFSK transmissions from ...
Brad's user avatar
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